Engineering plastics, such as polyamide, polyacetal, polyphenylene ether, polybutylene terephthalate, polycarbonate and polyphenylene sulfide generally have excellent mechanical properties, such as impact resistance, and thermal properties, such as heat resistance. Nevertheless they have problems of inferior processing properties and higher production cost. Moreover, some desired properties other than mechanical and thermal ones, for instance, chemical resistance or low water absorption, may not be included in with one ore more of the above-mentioned engineering plastics.
On the other hand, polyolefinic resins being typified by polypropylene, polystyrene resins being typified by polystyrene, and acrylonitrile-butadienestyrene (ABS) resins are inferior to the engineering plastics in physical properties, such as impact resistance and heat resistance, although they are excellent in processing properties and production cost. Polystyrene resins and ABS resins are amorphous resins and are inferior in solvent resistance.
Hence, many efforts have been made to blend or alloy two engineering plastics having different properties, to blend or alloy an engineering plastic and a polyolefinic resin, and to blend or alloy a polyolefin resin and a polystyrene resin, so as to complement with each other in their weak points and to produce resin compositions having new functional properties.
Simple blending, however, of two engineering plastics, of an engineering plastic and a polyolefinic resin, or of an engineering plastic and a polystyrene resin does not work well, and the resulting resin compositions have a lower impact resistance. When such blended resin compositions are molded, the molded products have problems of inferior appearance and interlaminer cleavage.
It is well known that such resin compositions can be improved in impact resistance to some extent by adding an elastomer component. The addition, however, poses a problem of reduced rigidity of the resulting resins. The problems of interlaminer cleavage and defective appearance, when such resins are molded, have not been solved.
To solve such problems, attempts have been made to improve the compatibility of resins to be blended by using a compatibilizing agent.
For example, for polyamide resins, a graft polymer which is formed by the reaction in the extruder between a polyamide and a maleic anhydride-modified polyolefin is used as a compatibility agent (Kobunshi-Kagaku, Vol. 29, p. 259 (1972)). Moreover, a compatibilizing agent is known, which is produced by mixing and reacting this system with a multifunctional compound that can react with carboxyl groups, carboxylic anhydride groups, amino groups and other reactive functional groups, to cause partial bridging (Provisional Patent Publication No. SHO-64-31864). With the use of this compatibilizing agent, resin compositions can be improved further in heat resistance and impact resistance.
To blend polypropylene with an engineering plastic such as a polyamide, a polyester, an aromatic polyether, a polyacetal, a polycarbonate or an ABS resin, it has been proposed to improve the compatibility of the resins by using a compatibilizing agent which is prepared by reacting an unsaturated acid- or anhydride-modified polyolefin with a low molecular weight diol, a low molecular weight diamine, or a low molecular weight compound having a hydroxyl group and an amino group, or if necessary, by using said compatibilizing agent together with an addition of a thermoplastic urethane (Provisional Patent Publication No. HEI-2-36248).
The use of the above-mentioned known compatibility agents, however, has not sufficiently solved the problem of compatibility of resin blends, and the resulting resin compositions have insufficient impact resistance. When such resin compositions are molded, they have problems of defective appearance and/or interlaminer cleavage. Moreover, depending on the type of compatibilizing agent used, a new problem was experienced; the resin composition itself was colored as a result of high temperatures used during molding.
The present invention was made in view of the above-mentioned problems of the prior art. The present invention is intended to provide thermoplastic resin compositions which have excellent impact resistance and heat resistance and, when molded, present good appearance without any interlaminer cleavage. Another object of the present invention is to provide new copolymers which are added to said compositions singularly or in combination, as compatibilizing agents.